Method of mixing and delivering aggregate mixtures



M rch 2 1962 M. M. TRUE 3,026,094

METHOD OF MIXING AND DELIVERING AGGREGATE MIXTURES Filed Jan. 20, 19594- Sheets-Sheet l FIG. 2

l0 I0 37 I3 l0 l5 l6 INVENTOR MAX M. TRUE M. M. TRUE March 20, 1962METHOD OF MIXING AND DELIVERING AGGREGATE MIXTURES Filed Jan. 20, 1959 4Sheets-Sheet 2 FIG.

ir Supply #To Front of Sump INVENTOR MAX M TRUE March 20, 1962 M. M.TRUE 3,026,094

METHOD OF MIXING AND DELIVERING AGGREGATE MIXTURES Filed Jan. 20, 195945 4 Sheets-Sheet 3 MAX M. TRUE March 20, 1962 M. M; TRUE 3,026,094

METHOD OF MIXING AND DELIVERING AGGREGATE MIXTURES Filed Jan. 20, 1959 4Sheets-Sheet 4 INVENTOR MAX M. TRUE United States Patent Ofifice3,026,094 Patented Mar. 20, 1952 3,026,094 METHOD OF MIXING ANDDELIVERING AGGREGATE MIXTURES Max M. True, P.0. Box 2526, Tulsa, Okla.Filed Jan. 20, 1959, Ser. No. 787,871 2 Claims. (Cl. 259147) Thisinvention relates to mobile mixers of the type that carry spraying orother delivery means for concrete or the like spray materials afteradding the required water to form the desired mixture wetness prior tofeeding it to a flexible hose for delivery to the place of applicationof the wet material to the building construction, and the method offacilitating such delivery, especially when a mixture of comparativelylow degree of wetness and high coarseness is used.

This application is a continuation-in-part of my pending application S.N. 558,765 filed January 12, 1956, now US. Patent No. 2,880,976.

The present spraying system and method is an improvement over previousmethods, which usually added the water to the dry mixture at the spraynozzle, thus causing incomplete mixture of improper proportions of waterwith the solid ingredients, and required experienced operators; and eventhen, these methods were very ineflicient and wasteful of water andcompressed air,

In the event the water was added to the mixture before delivery throughconduits to the spray nozzle, mixtures of low moisture content weredifficult to force through the conduits and would often pack in bends orelbows, causing interruptions in the work while the packs were cleared.

If the water was not added until the mixture reached the nozzle, a lotmore air was required to blow the dry ingredients through the conduitsto the nozzle, where dusting would also occur, and an excessive reboundor reject would result.

The main object of the present invention is to make it possible toefficiently handle wet mixtures of low moisture content after they havebeen thoroughly mixed with the correct proportion of water, and deliverthem in a desired spray for application to reenforced concrete layerconstruction or the like.

A further object is to mix the proper proportion of water with the dryingredients in a mobile mixer, and facilitate the delivery of slugs ofthis correct mixture from the mixer to the spray through a conduit byintroducing air under pressure in controlled amounts to the top of themixed batch in the mixer or to the conduit connection at the bottom ofsaid mixer, or both, depending on the fluidity of or degree of moisturein said mixture.

A further object is to use additional compressed air connected directlyto the spray nozzle to improve spraying of the slugs evenly over thework.

A further object is to provide piping assemblies and mixer blades on themobile mixer to facilitate carrying out the above objects.

A further object is to provide means including a piping system for a twotank mobile mixer to adapt it for use in the above process by using ahorizontally mounted common rotor shaft extending through both tanks andhaving peripheral mixing blades mounted thereon to thoroughly mix andsweep the correctly proportioned wet mixture in each tank in acirculatory path toward the adjacent ends of the tanks at the peripheryand in the opposite axial direction at the center, so as to continuouslyfeed the mixture past the sump outlets of the tanks at their adjacentends, the two sumps being connected to a selector valve for selectivelyopening one of the sumps to the spray delivery hose while closing theother sump, so as to enable the corresponding tank to be reloaded andmixed while the other one is sealed and used for supplying the slugs ofthe mixture under pressure through the sump to the delivery hose, thusproviding a continuous supply of freshly mixed wet mixtures to the spraynozzle upon demand.

A further object is to mount similar water and air supply and controlassemblies at the front and rear of the above mixer, each comprising aconnection from the air inlet through an air cut-off valve and a T, inseries to the inlet of a 3 way proportioning valve, the T, being alsoconnected to the water supply inlet, the two outlet ports of theproportioning valve branching off through a pipe line having a checkvalve to the top of the corresponding tank, and through a coupling andhose line to a check valve into the side of the corresponding sumpconnection opposite its outlet.

A further object is to provide hose connections between the otherconnections of the Ts connected to the air inlets and the water inletsof front and rear piping assemblies together for parallel operation, andto provide panels on the housings over the front and rear assemblies onwhich the corresponding proportioning and air cut off valve controlknobs may be mounted; and to provide a pressure gauge connected to thepressure control chamber and visible from the nozzlemans station.

Other and more specific objects will become apparent in the followingdetailed description of one form of the invention as illustrated in theaccompanying drawings, wherein:

FIG. 1 is a perspective view of a portable mixer incorporating thepresent invention,

FIG. 2 is a sectional view through one of the tanks showing the generalshape of the mixing blades and location of the sump connection,

FIG. 3 is a perspective view, partly in section, and broken away, of thesump piping connections,

FIG. 4 is a perspective view of the front piping as sembly, with air andwater supply controls,

FIG. 5 is a perspective View of the rear piping assemy,

FIG. 6 is an enlarged sectional view through the sump material feedvalve,

FIG. 6a is a front elevational view of the feed valve lever control,

FIG. 7 is a perspective view of the nozzle in action, and

FIG. 8 is a sectional view of another form of means for performing thenovel method of delivering the mixture in slugs separated by air slugs.

As a result of the use of spraying systems of the prior art, theconcrete structural jobs performed were plagued with tendency to formsand-pockets beneath and around closely placed reinforcing structure,and the water-cement ratio seemed to vary considerably, giving anuncontrolled variety of color, texture and strength.

The present system has not only eliminated these potential defects butis free of failures by clogging of the delivery conduits and is muchmore economical to make and to operate. It provides good embedment ofthe reinforcing structures both on vertical walls and horizontal slabs.Metered water and thorough premixing have been found to be essential toelimination of sand pockets and rebound, and quality controlledconcrete.

In using this system, a vibrating efiect is obtained at the nozzle, or asort of pulsation, which causes the concrete to flow around the steelreinforcement.

For purposes of illustration the present system is applied to adual-tank mobile mixer such as shown in FIG. 1, having rotating mixerblades 10 on a horizontal shaft 11 in coextensive substantiallycylindrical tanks 12 and 13 extending longitudinally of the mobilechassis 14 and having their sumps 15 and 16 at adjacent ends of thetanks connected to ports 17 and 18 in a common valve engineer'orarchitect over previous types of guns.

plate 19 leading through a selector slide valve to a conduit or hose 2%)'for delivery to the spray nozzle 21. The tanks are provided withindependent manhole covers 22 or doors on top for charging the dryingredient batches therethrough and sealing them for operation underpressure selectively, so that continuous nozzle operation is availableby premixing a batch in one tank while the material valve lever 23 ismoved in a position to open the sump of the other tank to supply thedemands of the nozzle operation.

Although it was necessary in previous nozzle constructions to usecompressed air fed directly to the nozzle for breaking up anddistribution of the material in the spray, the present system requiresonly a plain wedge shaped nozzle (not shown) which may be operated byinexperienced nozzlemen, because the air under pressure is supplied incorrect proportions to the top of the mixture in the tank and to thecorresponding sump connection in accordance with the flow-ability of acorrect low moisture content well-mixed concrete or other cementmixture, and the mixer blades passing over the sump provide anintermittent supply of the mixture and top air into the sump, while thesump air is added at 24 in sufficient quantity in slugs 62 underpressure to move the slugs 60 of the mixture through the conduits and tobreak them up at the nozzle into a homogeneous spray.

In order to provide this control and delivery of the V perfectlyproportioned and mixed materials through the nozzle we have inserted a lnipple 2 with 1" lines into each sump as shown whch allows a flow of airthrough this point when required. This is accomplished by the same meansof a proportioning valve 25. The purpose and accomplishment of thisimprovement is as follows: Whereas previous guns would not flow a realdry concrete or a real coarse aggregate because they plug up the sumpfrom air pressure pushing down on them, in the present gun the use ofthe bottom or sump air in combination with the top air allows us to blowany material from a complete dry state down the line to as much watercontent as is desired. In other words, when we blow a wet material, weuse top air only, and when we use a dry material, we use bottom air witha small amount of top air to keep the material .from floating in thetank. This works very nicely with no plug-up in the sump.

We have also changed the paddles, disclosed in our prior patentapplication Ser. No. 461,483, for Mobile Mixer, now Patent No.2,788,197, to further aid the gunning of this dry material. In otherwords, the paddles act as a distributor and actually deliver smallamounts or slugs of material into a rapidly moving stream of air in thesump causing a very slight pulsation in the hose line, which is veryimportant in keeping the materials from getting packed in the hose. Wefound out with any other type of paddles that the materials, such asRamsett and others as manufactured by Basic Refractories, Inc, wouldplug up in the hose unless we used the paddles that are shown in thedrawing, FIG. 2.

The gun is now really a concrete gun inasmuch as we can measure thewater exactly in our tank and give a guaranteed concrete. It is Wellknown that the previous type guns or dry mix-guns that are on themarket, cannot do this, as they guess at the required water at thenozzle, which produces a guess water mix. As is well known, concrete islargely a water-cement ratio mixture. It takes a certain amount of waterfor hydration of the cement in. the concrete, and then any excess of thewater causes voids in the concrete or weakens it, so that with our gunwe can establish the water-cement ratio because we measure the waterexactly in the dual tank chambers. This is readily acceptable to anyconcrete This also eliminates any sand pockets behind reinforcing steel,which is very frequently the case with the dry mix type of. guns,because they have a poor mix; as in the premixor wet mix each particleof aggregate is surround ed by cement paste and eliminates anypossibility of sand pockets.

Also through a wet mix gun such as this, we practically eliminaterebound. Rebound is caused because of a very poor mix of water andaggregate in the tanks and thus we practically eliminate rebound.

The important feature of the present gun over previous air guns is thatthey require a dry sand to go through their hose, and if too wet it willplug the hose. Our machine does not require a dry sand but will shootany sand whether dry, medium or wet. Proper reduction of the watercontent is accomplished by accurately reducing the amount of waterrunning into the tank.

Also our gun does not require a large compressor like the previous typesof guns. A compressor of c.f.m. of the gyro flow type, likeIngersoll-Rand manufactures, is large enough for the present gun. Theprevious type of guns requires a 315 to 600 c.f.m. compressor,consequently we can place concrete with an investment, including thetruck, compressor, conveyor and the complete ma chine, for about$12,000.00, compared to some previous types of guns with their 500c.f.m. compressor which costs about $15,000.00 by itself, and requires aconcrete mixer,- as they do not mix their material in the machine likeours, also a large truck and gun, the total investment for which isaround 3530,0000 for a comparable capacity.

Previous types of guns use all volume of air for conveying the materialssubstantially in suspension by the force of kinetic energy of the air.The present gun uses a combinationof air pressure and volume, thereforeless volume of air is required. To further explain the proportioningselector valve 25, this valve allows either a top air or complete bottomair, or any fraction of either one, or a combination of both. We callthis a selector valve. You will also note in the drawings that We havetwo panels 26*and 27, one for each tank. The top valve 25 is theselector valve, or proportioning valve, as it is set every day -for thetype of material you are shooting. If it happens to be a wet material,you use top air. If it is low slump material, you use about 70 lbs.bottom air and 50 lbs. top air. This of course really simplifies theoperation of this machine; The water is fed from a water hose connectedto a coupling 28 through the piping shown in FIG. 4, the cut-off valve29, the how meter 30, the T fitting 31, the individual water supplyvalve 29', the check valve 32 in either front or rear piping assembly, Tfitting 33, and then through the selector valve 25. A hose 34 may beused to interconnect the two T fittings 31 in the front and rear pipeassemblies. The check valve 32 stops the water from going into a tankthat is under pressure also because of the air pressure, and the waterruns into the other tank which is desired.

Referring to the booster air valve 36, it may be coupled to an air hose55; as shown in FIG. 7, and is mounted on the nozzle 21 for supplyingadditional spraying air to the nozzle when more dispersion is desired.

By proper adjustment of selector valve 25, both bottom air and top airis used to aid in feeding a low moisture content material such asconcrete or refractories of 8% moisture approximately. Bottom airpermits the material to move out ofthe sump. Top air feeds the sump andproduces slugs of material intercepted by volumes of compressed air.Without bottom airthe sump will pack, without top air the material willfloat. So therefore a combination of bottom and top air feed isrequired. The paddles 37 operating over the sump act as a distributorand permit intermittent feeding of slugs of materialand air. Thus thehosev will not plug up and when the material valve is shut oti at thetank the sump is emptied by the continued flow of. compressed airthrough air lines 75 to the front of the sump. A nozzle with added airis not ordinarily necessary as the air introduced in the hose betweenthe material wads is suflicient to break up the material in a nice sprayand only a wedged pipe nozzle is required.

The top air is used for pushing by pressure a material that flowsthrough the hose. The combination top and bottom air carries the harderflow or low moisture content material through the hose in a volumemethod of wads of material and pockets of air. This is accomplished by aselector or proportioning valve 25, which introduces top and bottom airto provide the correct pressure and flow. We eliminate dusting andrebound that is common in other known sprayer systems, because ofpremixing.

This machine will feed material of any low moisture content down to aperfect dry by using the combinations of air mentioned.

The nozzle man does not have to have any control over the quality of theconcrete because it is controlled at the machine. Therefore a trainedman is not necessary. The nozzle man, in some known systems, adds thewater at the nozzle and has a guess control of the quality of theconcrete. An experienced nozzle man is therefore required to operatethat type of machine. Usually 2 to 3 years experience is necessary, andstill they guess at the water amounts.

The present machine will also sand blast wet or dry, by using a regularsand blast nozzle.

Due to the slugs of properly premixed material, it traps the air andconserves it. Accordingly, only a 125 c.f.m. air compressor is requiredto blow the material through the 1 /2" hose where some other systemshave to have a compressor 4 or 5 times this capacity. The so called drymix guns of the prior art carry their material through in a dry stateand mix water at the nozzle, therefore they waste a considerable amountof the air and require a 315 to 600 c.f.m. air compressor to do the samevolume of work as the present syrayer system.

The premixing gives controlled concrete. Others guess at the watersupply at the nozzle and do not have controlled installations. We canuse wet sand, others have to dry their sand for sand blasting or forconcrete work. They pick up drift or sand pockets in the concrete,shooting around reinforcing steel, because of the poor mix. Thepremixing eliminates sand pockets.

Each pipe assembly on the front and rear of the machine is similarlyoperated and constructed. The selector valve 25 is a 3-way valve withtwo adjustable ports to the tank and sump lines respectively, to providevariations in the amounts of their opening, or to close one or the otherentirely, while maintaining the supply port at the bottom of the valveopen all the time. The hand wheel valve 38 is a three way cut-off valvefor the compressed air which is supplied from the compressor by a hoseline connection through main air supply valve 39 and the regulator 49,shown in FIG. 4, to the cut-off valve 38 in each pipe assembly, by meansof the T-fitting 40 (FIG. 4). A hose line 41 may be connected betweenthis T-fitting 40 and the cut-off valve 38 in the rear pipe assembly. Asafety pressure relief 42 may be provided in the air supply line with amanual relief control 43 which may have a pull string tied to it andextended to a convenient place on the front control panel 27 foroperation therefrom. A pressure gauge 44 may also be suitably mounted onthis panel for indicating the regulated air pressure delivered to theair supply line, the regulation of this pressure being provided, asalready mentioned, by the regulator 49. Check valves 45 are provided inthe lines from the selector valves to the tanks to prevent returnleakage from one tank back through the pipe assemblies to the other tankto interfere with the water feeding into the latter, when the air supplyis out OK.

The flowmeter 30 has a continuous indicator dial 46 to enable theoperator to supply measured amounts of water to the mixes as may berequired.

FIG. 7 illustrates a plain nozzle 21 in use in applying a premixedmaterial 53 to a reinforced wall construction 54. A hose 55 may beconnected to the valve 36 to supply additional spray air to the nozzle21 when desired.

The method of delivering the mixture in slugs separated by slugs ofcompressed air may be performed by other means than the arrangementshown in the above described apparatus. One such means is illustrated inFIG. 8, wherein the bottom of each sump 64 from any mixture supply tank65 may be provided with an auger type feeding worm 67 or a pump pistontype (not shown) feeding means for providing a continuous supply of themixture to the outlet port 66 which is connected through the materialvalve 68 to the delivery hose 20. An air pulsator 70 is connected to theoutlet port 66 for feeding slugs of compressed air 62 at controlledintervals as may be required for any particular mixture to form theslugs of mixture 60 and facilitate their movement through the deliveryhose and spray nozzle to the work. In this case the top air pressure isnot required in the tank 65, if the auger worm is relied on for feedingthe mixture under sufiicient pressure.

It is to be understood that this novel method and apparatus is adaptablefor supplying cement, aggregate and water mixture of any type as well asother wet or dry mixtures of any fluidity, which are to be applied toany surface by spraying thereon.

This invention is particularly adapted for comparatively dry mixtures oflow fluidity which could not otherwise be forced to flow through thedelivery hose because of the high friction and resistance to flowespecially around bends in the hose.

The injection of the air slugs reduces the total resistance to flow inthe entire length of the hose and requires a reasonably reduced airsupply pressure, while still permitting a substantially continuous anduniform spray from the nozzle 21 at the end of the hose, by suitablyreducing the size of the individual slugs of material and air.

The amount of air required in the present method is very small comparedto some of the prior methods of delivering dry ingredients of themixture by blowing them through with a large volume of air. These priormethods, which relied on adding the water to the mixture in the spraynozzle, were very wasteful of the mixture ingredients also, because ofpoor mixture with the water and poor adhesion to the work. Sand pocketsin the work were almost impossible to eliminate, and proper watercontent was difficult, if not impossible, to control by these priormethods, resulting in poor quality work. Also structural engineers cannow design structure around the present gun but could not do so withother types, such as the dry mix guns.

The present method uses properly proportioned mixtures of exact Watercontent and permits its delivery through a long flexible hose to do agood job efficiently in remote and hard to get 'at places by unskilledpersonnel.

The feed tank selector valve may be made as shown in FIGS. 6 and 6a. Arotatable plug 72 in which the angular port 7-1 is located, is connectedby means of the stud 'bolt 73, operating in arcuate slot 74 in the valvecasing 76, to an arm 77 of a rotatably mounted plate 78 on the front ofthe valve casing 76. This plate has the control lever 23 firmly fixed toit so as to rotate the port 71 selectively into communication with sump15 or sump 16 at its inner end while its outer end remains axiallyaligned in communication with the entrance to the feed or delivery hose20.

Many obvious modifications in the form and arrangement of the parts maybe made without departing from the spirit and scope of this invention,as defined in the appended claims.

What is claimed is:

1. The method of facilitating the delivery of a readymixed,high-density, low water content cement-aggregate-Water mixture through aflexible flow line for remote application, comprising impelling a flowof said mixture into the feeding end of said flow line, reducing thefrictional drag on the material in said flow line "by injecting slugs ofair thereinto of such size and frequency 5 as to decrease the density ofthe material per unit length by the provision of a plurality ofalternately arranged slugs of air and material per said unit length.

2. The method defined in claim 1, and regulating the size of said slugsof air and mixture to such a reduced 10 length as to provide asubstantially continuous and uniform flow from said flow line.

References Cited in the file of this patent UNITED STATES PATENTS DiSanto et al Nov. 4, 1941 Thompson Feb. 21, 1956 Skeggs June 25, 1957Hale Oct. 28, 1958 True Apr. 7, 1959

